▲Batteries Not Included, or Required, for These Smart Home Sensors(coe.gatech.edu)
59 points by gnabgib 2 days ago | 8 comments
▲harg 2 hours ago
There already exists "kinetic" switches for lights etc whose switch contains some passive electronics that when actuated produces enough energy to emit a radio signal that can be read by a relay module. They're pretty handy as you can basically place the switch anywhere you want without the need for the wires to be there. The relay can live in the light fitting or somewhere else convenient.

There's probably no reason why these kinetic switches can't also be used for detecting other events like doors opening/closing etc. I feel like a radio signal is a bit more reliable and easier to detect than high frequency sound.

I also think calling these a "sensor" is a bit of a stretch. They detect events but have no knowledge of the current state of the thing they're sensing. E.g. the can detect a door opening/closing, but have no idea if the door is open or closed at a given time

▲buescher 2 hours ago
Piezo harvesting switches and similar (I think there’s a flywheel design out there too) are quite expensive, not terribly reliable or consistent, and require substantial activation force. Conventional switches and batteries that can last for years in remote push buttons and sensors are extremely inexpensive in volume.
▲Terr_ 1 hour ago
> for detecting other events like doors opening/closing etc.

If any of those doors are important for security, then I'd want something an intruder can't easily jam or spoof.

▲anVlad11 1 hour ago
It's research, not a product. Even with that, framing it as a smart home sensor in the press release is a stretch.

1) 93.75% success rate in controlled conditions, 92.1% in a somewhat-realistic deployment scenario - too low for reliability. I wouldn't use something like that to trigger smart home automations.

2) Range hardcapped at ~1m due to how ultrasound works, you can't centralize detection. Their answer is to give everyone in the household a wearable receiver, which is eeeeeeeh idk, doesn't look consumer-friendly to me.

3) Paper suggests a mix of durable and consumable parts for the transmitter. Their numbers show that the 3d-printed PLA cantilever needs to be replaced every 900 cycles or so. Should work fine, but...

4) ...every transmitter pair needs to be tuned per-setup, every time. Not a plug&play in the consumer sense.

▲cucumber3732842 1 hour ago
From the artwork it looks like they're targeting industrial use. Seems like a low grade replacement for bar/qr code scanning. The "wearable" (more likely integrated into some other thing than worn IMO) receiver seems to point in that direction too.

Author probably has a specific use case in mind. Probably some application where EM emissions are undesirable or power is complicated that has thus far resisted automated industrial data entry. Investigating the use of something like ultrasound would align with constraints like that. Someone (department head? PR department?) said that was too niche and to make up some bullshit with mass market appeal.

▲ogig 2 hours ago
I can see some uses, but calling this system batteries free seems a stretch. A sensor is worth nothing if it can't be read, and to read this you need a powered microphone and computing. Some already common magnetic door systems do the same; door plate and magnet movement is enough to create a detectable current, (using no external power), then that signal is read and computed by an electronic/digital system (using power).
▲SOLAR_FIELDS 1 hour ago
Even the layout you describe has massive advantages over the status quo from a placement perspective. Having a reduced footprint device that goes in the actual measurement location that can phone home to a more robust central location like this is not only already very common but also the existing solutions that do it still suffer from the design constraint of requiring a battery which this innovation goes a long way towards
▲phh 2 hours ago
I'm on the side of "clever, fun, but feels useless". But to defend the project, all sensors require a powered central system. It's pretty common for Zigbee to have one repeater per room [1], which is just what is needed for this system.

[1] Because any AC-powered Zigbee device is a repeater, so just a bulb or a plug is enough

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▲combocosmo 2 hours ago
It's a unique idea that I could see being useful in select situations. The reliance on wearable microphones sounds like a downside.

Also I guess this might be annoying for pets that can hear well beyond 20 kHz.

▲kumarvvr 1 hour ago
Would these maintain their signature under repeated use? Or regular wear and tear?
▲tetris11 2 hours ago
Im not sure I got it. It generates acoustic signals and a microphone server picks them up.

If so, will it penetrate through walls?

▲lesuorac 29 minutes ago
Well, idk if these do but you can certainly make passive devices that penetrate walls.

See http://en.wikipedia.org/wiki/The_Thing_(listening_device)

▲croes 2 hours ago
Unlikely because it’s ultrasonic sound, at least if you have brick walls.

Could work for drywalls

▲fragmede 2 hours ago
The microphone is on a smart watch the user is wearing.
▲croes 2 hours ago
Do you need a signal that tells you the window is open if you are in the same room?
▲SimplyUnknown 2 hours ago
Obviously not, but there is larger potential than that. A microphone in a watch or phone can pick up the signal and relay the trigger to another server via for example MQTT. Then, you can have homeassistant act upon this signal.

The flow is then Open door --> Signal triggers --> Signal caught by microphone --> Microphone device relays to server --> Server turns on smart lighting in that room.

There is a lot more that you can do, but this is just an example. The microphone to pick it up is a limitations, but the gain is:

- reduced power usage as the signal generators are not power-operated

- less waste as no empty batteries need to be discarded (if non-rechargeable batteries are used)

- improved security because the signal generators are not connected to the internet, reducing the attack surface.

▲hilti 2 hours ago
If you are constantly looking at your smartphone and ignore the real world ... yes ;-)
▲cyberax 2 hours ago
Trivia time! The first practical wireless remote control for TVs also used ultrasound: https://www.youtube.com/watch?v=MLPk1Us62xQ
▲buescher 2 hours ago
Right, and they were superseded by battery-powered infrared remotes for good reasons. I would recommend revisiting those reasons before proposing this sort of technology for wireless sensors.